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IHateMyJob2004
05-17-2009, 06:51 AM
I have a 2003 Chevy 1500 (RWD) with about 120K miles on it.

Several days ago, I noticed that at around 30 mph it shakes a bit. The shakes seam to be coming from the rear of the truck. This shaking does not occur at 20 mph or 40 mph. Just 30 mph +/- 5 mph.

So, is this just something wrong with my tires or is there a more serious issue? I'm thinking about taking it to a shop but am curious about what this could be.

There does tend to be some sort of noise associated with this problem. Can't pinpoint what it is.

For now, my wife isn't allowed to drive it.

EDIT 1:
OH, When I'm braking at very low speed (10 mph even) there seems to be some sort of problem related to the shaking that is also new.

Recently, I rotated my tires and checked the brake pads and they have plenty of life left in them. The rear rotors are new (10K miles) and the front are original to the truck (thinking about replacing them soon just as preventative maintenance). Since the rear rotors are newer and the pads are fine I have a hard time believing that the shaking which seams to be coming from the rear is brake related.

EDIT 2:
This also happens at very low engine RPM (1300 maybe). I haven't checked to see if this is evident at a faster speed and low engine RPM. But when braking at 10 mph, I'm sure the RPMs are also low.

EDIT 3:
I should say that at just the right speed, the truck shakes alot. It's very noticeable in the cab.

From some internet searching. Some ideas. Bent drive shaft, maybe. Alignment, I doubt it. torque converter in transmission, what?

Analog
05-17-2009, 07:37 AM
You said you just rotated the tires. Have they been balanced too? You might have an imbalance on both rear tires that demonstrate a harmonic at a certain rotational speed.

Have you tried getting this to occur at 30MPH and then put the vehicle in neutral to see if it continues? That would eliminate some of the drivetrain components.

Also, does this occur on a wide curve? Like on a highway on-ramp? This would give you some differential speed between the rear wheels.

IHateMyJob2004
05-17-2009, 08:04 AM
Neutral is a good idea. I'll try that today.

I'll check deceleration and acceleration at 30 mph some more.

This happens when I am going straight or on a curve. It does not discriminate ;)

The tires are balanced. I simply rotated them.

Sluggo
05-17-2009, 09:56 AM
If its an extended cab, check the mid-line driveshaft bearing.

Actually they all might have that bearing, I never looked under any but mine.

Engineer
05-17-2009, 10:59 AM
Do you get the same shaking at 60 mph? As Analog stated, it could be an imbalance from your rear tires and if it occurs at 30, it will also occur at 60 and 90 (harmonic frequencies). I don't ever recall having an imbalance at 30 mph on any of my cars and it seems sort of low. Most balance issues that I've seen seem to be near the 60mph range but it's certainly possible.

IHateMyJob2004
05-17-2009, 03:28 PM
I doubt it has to do with tire balance issues. It wasn't there when I left work (city driving). Then I was on the highway. Then I got off the highway near my home and I was like, what the hell is that?

Yes, it is an extended cab.

I'm starting to think that the universal joint is shot. Of as Sluggo mentioned, it might be the mid-line driveshaft bearing ... whatever that is.

I did do some tests. In neutral, it shakes at 30 mph.

There is also a noise associated with this. It really sounds like ball bearings that are gone somewhere. Or the universal is sloppy (loose). There are two noises. It is either a creeky noise (not sure what to associated it with) or a screeching noise. The screeching noise is much like the noise that would occur if your brake pads need replacement. I rotated the tires a few weeks ago because I thought the pads were shot. So it was going to be a tire rotation/pad replacement job. During rotation, I realized the pads are less than half way through their life.

I haven't gone 60 mph since these problems started. That will be in the morning tomorrow. I'll be calling a shop near where I work to see if they can look at it. At 40 mph though, no shaking and the noises almost seem to go away.

What is the gear box called that the drive shaft connects to on the rear axle?

I'll keep people up to date on my fun. and costs.

Sluggo
05-17-2009, 04:56 PM
Originally posted by: IHateMyJob2004

I'm starting to think that the universal joint is shot. Of as Sluggo mentioned, it might be the mid-line driveshaft bearing ... whatever that is.




You have a 2 piece driveshaft. It is supported in the middle (to keep all the weight of the driveshaft resting on the u-joints) by a bearing in a rubber and metal carrier thats bolted to the frame. If you can grab and shake the driveshaft and see some movement in this bearing/carrier it has gone bad and will have to be replaced. Its not a DIY project unless you have a bearing press. Most shops will do this pretty cheap, but while its there, you should just have the whole driveshaft rebuilt, and rebalanced. You can pull the driveshaft yourself and just carry it in for service.

Squisher
05-17-2009, 06:13 PM
Don't discount the out-of-balance or belt-shift problem with a tire. When you moved the tires to the rear they became much less loaded with weight and any problem with them would become more noticeable. If anything, it is the cheapest and easiest place to start. Discount Tire is pretty cheap for this, if you have one in your area.

Corn
05-17-2009, 11:01 PM
Double check to make sure the parking brake is not engaged. Also, could possibly be a bent wheel/balance issue.

imported_elwood
05-18-2009, 12:28 AM
My 91 ranger was doing the same thing a while back. I brought it to a local mechanic and he changed the u-joints on the drive shaft (thats what i figured it was) and some pin in the rear end (can't remember). $130 and it was good as new.

joutlaw
05-18-2009, 08:59 AM
Could be U-Joints or the carrier bearing. It could also be the pitman/idler arm. Get your wheels balanced first though.

IHateMyJob2004
05-18-2009, 09:01 AM
Only happens at 30-35 mph. Not at 60-70 as some thought might happen.

I'll get underneath in a few hours and see if the drive shaft is sloppy.

EDIT: Have an appointment with "the shop" on Tuesday morning.

IHateMyJob2004
05-19-2009, 12:31 PM
And the answer is ........ the front tie rods need replacement.

Also, my pumpkin (differential housing) has a leak and is getting repaired. That might be where the noise I heard was coming from.

boomerang
05-19-2009, 02:54 PM
Originally posted by: IHateMyJob2004
And the answer is ........ the front tie rods need replacement.

Also, my pumpkin (differential housing) has a leak and is getting repaired. That might be where the noise I heard was coming from.
Thanks for posting back with the results. :)

Engineer
05-19-2009, 04:50 PM
Originally posted by: IHateMyJob2004
And the answer is ........ the front tie rods need replacement.

Also, my pumpkin (differential housing) has a leak and is getting repaired. That might be where the noise I heard was coming from.

I was completely thrown off when you stated that you thought that the shaking was coming from the rear of the truck (not that I would have necessarily known anyway, lol! :P )

I replaced tie rod ends once. Not that bad of a job really. Everything was pretty good until I took it to be aligned after I changed them and the car pulled from that point forward, no matter how many times I tried to have them correct it, lol! (I counted threads (turns) on my initial installation and it was much better than anything they did).